Coil support for electrical measuring instruments



June 6, 1950 wo E z 2,510,733

COIL SUPPORT FOR ELECTRICAL MEASURING INSTRUMENTS Filed March 24, 194'? Patented June 6, 1950 UNITED STATES PATENT OFFICE COIL SUPPORT FOR ELECTRICAL MEASUR- ING INSTRUMENTS I Alfred H. Wolferz, Hillside, N. J., assignor to Weston Electrical Instrument Corporation; Newark, N. 3., a corporation of New Jersey.

Application March 24, 1947, Serial No. 736,833

1 Tins-invention relates to electrical measurin instruments and in particular to instruments of the dynamometer type.

In manufacturing instruments of the class described, especially those of the multiple element type in which the moving system includes a pair of coils mounted in-line such as polyphase wattmeters and the like, considerable difliculty has been experienced in the design of the mechanism by which electrical connections are made from fixed terminals inside of the instrument casing to the coil or coils. A pair of extremely flexible spiral springs of conductive material have in general been found best suited for this purpose and the usual practice has been to mount these springs outside of the coils along the staff axis. However this arrangement is not entirely satisfactory and is of considerable disadvantage in the case of multiple element instruments since the overall staff length is thereby unavoidably lengthened by the amount necessary to accommodate the spiral springs.

The object of this invention is to provide an improved mounting for the conductor springs, the latter being arranged inside of the coils. The new arrangement has many advantages not found in the prior constructions among which are, good insulation between the springs and staff, a shorter staff, and more economical construction. Other objects and advantages will become more apparent from the accompanying drawings of which Fig. 1 is a side elevation of the improved construction as applied to a polyphase wattmeter; Fig. 2 is an enlarged view in side elevation of the coil and internally mounted springs; Fig. 3 is a top plan view of the coil and springs shown in Fig. 2; and Fig. 4 is a transverse sectional view taken on lines 4-4 of Fig. 2.

Referring now to the drawings, the instrument coil I as shown is somewhat elongated and is comprised of a plurality of conductor layers which are preferably wound on an arbor having bushings 2 and 2 of insulating material mounted thereon. After the coil has been wound, the arbor is removed leaving the bushings 2 and 2' which are aligned along the axis on which the coil is to be rotated. The bushings are then fixed fast to the coil such as by cementing them in place.

Spiral springs 3, 3' of conductive material through which the electrical connections are made between coil I and fixed terminals inside of the instrument casing are mounted within the coil, the inner ends 4, 4' of the springs being fastened to axially extending tongues 5, 5' on terminal sleeves 6, 6 of conductive material that are press fitted respectively on the bushings 2, 2 and'lie in abutment with .the inner faces of collars'l, 1- formed on the bushings. The sleeves 6, 6 are also provided with transversely extending tongues 8, 8' to which the lead-off ends 9, 9 of the coil I are connected. In the illustrated polyphase Wattmeter application of the invention, and referring now in particular to Fig. 1, two of the coil and conductor spring sub-assemblies as shown in Fig. 4 are placed in position with the other components of the meter such as the stationary coils III which produce the magnetic fields that control the angular movement of the coils I, I, and a single staff II is then inserted through the bushings 2, 2' of both coils, the staff being thereafter mounted at its ends in jewelled bearings of conventional construction.

The outer ends I2, I2 of the spiral springs 3, 3 at each of the coils I, I' are then fixed to stationary terminals I3, I3 in the instrument from which connections are made in the usual manner through the necessary shunts to binding posts located on the outside of the instrument casing.

In conclusion, it will be seen that the improved construction according to this invention has many advantages. Assembly of the complete instrument is simplified since the coil and conductor springs may now be made up as a sub-assembly which saves times and thereby reduces instrument cost. For dual element meters, a single staff can now be used thereby replacing the more expensive and less desirable two piece construction where the two shaft sections were joined by an insulator on which the springs were mounted. Mounting the springs internally of the coils rather than outside of them also makes it possible to use a shorter staff thus saving considerable space (as measured along the axis of the moving system) which is most important in multiple element instruments such as the illustrated polyphase wattmeter because it enables one to use a much smaller casing that compares more favorably in size with the other types of measuring instruments using but a single movable coil.

Further it will be evident that the improved coil and spring construction may be applied equally as well to other kinds of dynamometer instruments and that various changes in the construction and arrangement of parts may also be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In an electrical instrument, a coil adapted to be rotated on its axis, a pair of insulating bushings extending through said coil on opposite sides thereof, said bushings being aligned along the coil axis and adapted to receive a staff, a pair of conductive spiral springs within said coil, a conductive sleeve carried on each bushing, each said sleeve being fixed to the inner end of one of said springs and electrically connected with a lead-off from said coil, and stationary terminals securing the outer ends of said springs.

2. The invention as defined claim 1 wherein each sleeve is provided with axial and transverse tongues, the inner end of the associated spiral spring being fixed to the axial tongue and a coil lead-oil being connected to the transverse tongue.

3. The invention as defined in claim 1 wherein 4 bushings, a coil supported by said bushings and adapted to rotate on the bushing axis, a pair of conductive spiral springs within said coil, and a conductive sleeve on each bushing fixed to the inner end of one of the springs and electrically connected to a lead-off from said coil.

ALFRED H. 'WOLFERZ.

REFERENCES CITED The following references are of record in the file of 'this patent:

UNITED STATES PATENTS Number Name Date 1,764,363 'Stalder June 1'7, 1930 2,077,136 Rich Apr. 13, 1937 FOREIGN PATENTS Number Country Date 456,988 Great Britain aha. Nov. 1-9, 1936 

